The present invention relates to ventilators, more particularly but not exclusively for use in rooms with sealed windows and/or double glazing where it is desirable to provide ventilation without having to open the window. This type of ventilation is now usually referred to as "secondary ventilation".
Secondary ventilation is often achieved by the insertion of a slot ventilator into a slot cut or formed in the sash of a window, the slot connecting through an air passage usually to the exterior of the building. Air flow through the resulting ventilation passage is controlled by some sort of openable or closable ventilator such as a hit and miss ventilator or a parallel motion ventilator of the type described in UK patent 1417751.
While the known type of parallel motion ventilator has been found to be excellent in practice, there are certain specific situations in which yet further improvements can be made. Firstly, it has been found that the "throw" of the ventilator, in other words the distance forward of the main ventilator body by which the facing strip or closure member has to be moved in order fully to open the ventilator, can be further reduced by means of an improved linkage, making it even less likely for a user accidentally to snag the closure member when it is in the open position. Furthermore, the applicants have now found a way to increase the effective air opening of the ventilator without reducing its size.
The other type of known ventilator, the so called "hit and miss" ventilator , has to be relatively large in relation to its air opening since the configuration of the ventilator itself cuts down the air flow. This type of ventilator comprises a fixed slotted panel mounted over an aperture, for example in a window sash, with a similar slotted panel arranged for sliding movement with respect to the fixed one. In the open position of the ventilator the slots in the two panels line up, so allowing air to pass, whereas in the closed position the slots in one panel line up with the bars between the slots of the other. As will be evident, the maximum air flow through a ventilator of this type is very substantially less than the maximum air flow which could otherwise flow through the aperture on which it is mounted; less than 50% would be a typical figure.
The known ventilators, then, if they are designed in order to allow through them a specified air flow, must be provided with an aperture in the window which is larger than would actually be needed to support such an air flow in the absence of the ventilator. This has tended to mean that known ventilators, especially the hit and miss type are excessively bulky for the air flow that they actually allow through. In recent years, this problem has become more acute as manufacturers of timber windows try to save as much timber as possible by providing only a very narrow sash between the glass and the window frame. This has meant that the apertures in such sashes, which have to be provided with ventilators, are now very narrow, with little space between the edge of the aperture and the frame for a bulky ventilator to be positioned. In addition, the head profiles of modern windows (that is the distance between the surface of the sash and the surface of the frame, in a direction perpendicular to the glass) are very narrow. For both practical and ascetic reasons it is not desirable to have any part of the ventilator, either in the open or in the closed position, which extends forwardly of the surface of the frame. This of course restricts the length of the throw.
It is an object of the present invention at least to alleviate at least some of the difficulties of the prior art.
It is another object of the invention to provide a compact controllable ventilator which allows through it all, or substantially all, of the air flow capable of passing through the aperture to be controlled.